Ion clustering in aqueous salt solutions near the liquid/vapor interface

TL;DR

This study uses molecular dynamics simulations to explore how different salts influence the structure and roughness of the liquid/vapor interface in aqueous solutions, revealing ion-specific effects on clustering and surface properties.

Contribution

It provides new insights into ion clustering behavior and surface roughness variations near the interface, considering charge transfer and polarization effects in the models.

Findings

Larger ion clusters form in bulk but less at the interface.

Chloride salts reduce surface roughness compared to pure water.

Iodide salts increase surface roughness, indicating higher surface affinity.

Abstract

Molecular dynamics simulations of aqueous NaCl, KCl, NaI, and KI solutions are used to study the effects of salts on the properties of the liquid/vapor interface. The simulations use the models which include both charge transfer and polarization effects. Pairing and the formation of larger ion clusters occurs both in the bulk and surface region, with a decreased tendency to form larger clusters near the interface. An analysis of the roughness of the surface reveals that the chloride salts, which have less tendency to be near the surface, have a roughness that is less than pure water, while the iodide salts, which have a greater surface affinity, have a larger roughness. This suggests that ions away from the surface and ions near the surface affect the interface in opposite ways.